1. Field of the Invention
This invention relates to a method and apparatus for recording and/or reproducing data for a signal recording medium.
2. Description of the Related Art
In a data recording and/or reproducing apparatus, employing a disc, there is known such disc in which a servo field is provided in a sector of a recording track of the disc, as exemplified by a hard disc. Recently, this technique is exploited in a flexible disc configured to accommodate the high density recording.
In a data recording and/or reproducing apparatus for recording and/or reproducing a flexible disc having a servo field, servo for seeking a target track for a magnetic head or servo for on-tracking is applied, or data is reproduced from a data field provided in association with a servo field, by signals recorded in the servo field.
In the servo field, there are recorded SYNC, servo timing marks (STM) and gray codes and servo information (A-burst, B-burst and so forth). The data recording and/or reproducing apparatus applies synchronization by SYNC and acquires recording/reproducing timing by servo timing marks. On the other hand, the data recording and/or reproducing apparatus recognizes the track positions on which is located the magnetic head, by the gray code, to correct the position of the magnetic head by the A-burst, B-burst etc.
In the data field, there are provided the SYNC and a data area. The data recording and/or reproducing apparatus applies synchronization by SYNC to read out data. Specifically, for data readout, a read-out gate of a read-out circuit is opened after lapse of a certain time, with the servo timing mark in the servo field as a reference, to read out data in a data area. That is, the read-out gate is opened so that the magnetic head is able to read from the SYNC of the data field to read-in data from a data area next following the SYNC.
It is noted that reflection of the results of inspection of the product quality after manufacture on a product after the inspection is crucial by reason of maintenance of data quality. For example, inspection of defective sectors of a disc to hold the defective sector position on the disc as the results of the inspection and reference to the results of the inspection to have data recorded and/or reproduced only on or from valid sectors represent effective means to prevent data recording and/or reproduction from becoming infeasible.
On the other hand, even in a disc decided to be free of defects by quality inspection, it is a frequent occurrence that sector errors be produced in an acquired fashion due to scratches on the disc surface, caused by repeated use, variations in the apparatus used for recording and/or reproduction, or to changes in the disc using environment, such as changes in temperature or humidity. For example, there are occasions wherein servo timing marks (STM) become unreadable due to scratches on the disc surface. If the servo marks become unreadable, the read gate becomes unopenable after lapse of certain time as from this servo timing mark as a reference, with the result that even normal data with only low inherent ECC error occurrence probability become unreadable.
Thus, it is thought to be desirable that data in the data field be made readable in case servo timing marks become unreadable in an acquired manner and that the read gate become unopenable after lapse of a certain time as from this servo timing mark as a reference such that even normal data with inherently low ECC error occurrence probability become unreadable.
Under the above-described circumstances, there is a demand for enabling data in the data field to be read in case the serving timing marks become unreadable in an acquired manner, and for having defective sectors supervised strictly at the time of manufacture. If the defective sectors can be made detectable by exploiting the functions in the apparatus, the apparatus can be exploited more efficiently.
It is therefore an object of the present invention to provide a data recording and/or reproducing apparatus in which, even on occurrence of readout droppings of the servo timing marks, next following normal data can be read, and in which defective sectors can be strictly supervised at the time of e.g., quality inspection.
In one aspect, the present invention provides a data recording and/or reproducing apparatus for recording and/or reproducing data for a recording medium having a sector including a servo area carrying servo signals used for servo and a data area provided in association with the servo area, including control means for opening a read gate at a first timing associated with a timing reference signal recorded in the servo area to reproduce data from the data area if the timing reference signal has been detected with success. The control means opens the read gate at a second timing associated with a timing reference signal detected from within a servo area of a previous sector to reproduce data from the data area if the timing reference signal has not been detected with success.
On detecting a defective sector, the control means opens the read gate at a third timing different from the second timing if the timing reference signal cannot be detected to detect the defective sector of the recording medium.
In another aspect, the present invention provides a data recording and/or reproducing apparatus for recording and/or reproducing data for a recording medium having a sector including a servo area carrying servo signals used for servo and a data area provided in association with the servo area, including control means for opening the read gate after lapse of a pre-set time duration after detection of a timing reference signal recorded in the servo area for reproducing data from the data area, if the timing reference signal has been detected with success. The control means outputs a pseudo timing reference signal based on a timing reference signal detected from within a servo area of the previous sector if the timing reference signal has not been detected with success. The control means opens the read gate after lapse of a second time duration after detection of the pseudo timing signal to reproduce data from the data area.
On detecting a defective sector, the control means outputs a pseudo timing signal based on a timing reference signal detected from within a servo area of a previous sector if the timing reference signal has not been detected with success. The control means opens the read gate after lapse of a third time interval after detection of the pseudo timing signal to reproduce the data from the data area.
In yet another aspect, the present invention provides a sector defect detection method for a recording medium having a sector including a servo area carrying servo signals used for servo and a data area provided in association with the servo area, including detecting a timing reference signal recorded in the servo area, outputting a pseudo timing reference signal, based on a timing reference signal detected from within the servo area of a previous sector, if the timing reference signal has not been detected with success, opening the read gate after lapse of a pre-set time after outputting of the pseudo timing signal to read out data from the data area, and decoding the read-out data to check a defect. The time which elapses since outputting of the pseudo timing signal until opening of the read gate is set so as to be longer than the time which elapses since the outputting of the pseudo timing signal in case of failure to detect the timing reference signal until opening of the read gate.
The data recording and/or reproducing apparatus according to the present invention includes a controller having a function for opening a read gate at a timing associated with a timing reference signal recorded in a servo area to reproduce data from the data area and for opening the read gate at a timing associated with the previously obtained timing reference signal to reproduce data from the data area if the timing reference signal has not been detected with success. When a defective sector is to be detected by the control means, the above-mentioned function is turned off to detect the defective sector. If the timing reference signal has not been detected, the function of opening the read gate at a timing associated with the previously detected tinning reference signal to reproduce the data from the data area to detect the defective sector of the recording medium.
Thus, for quality inspection, it is possible with the data recording and/or reproducing apparatus to detect the defective sector by having its function of reproducing data from the defective sector turned off
Therefore, with the present data recording and/or reproducing apparatus, it is possible not only to record and/or reproduce data for the data area, but also to detect defective track, even if the servo timing mark cannot be read out.